In just a week, the dollar has gone from a safe haven to investors' whipping boy as US President Donald Trump's chaotic tariffs on friend and foe alike undermine decades of trust in the world's reserve currency.

The sudden loss of confidence was nowhere more stark than in the Treasury market, which saw the largest weekly increase in borrowing costs since 1982 as offshore funds fled. "The US, almost overnight, it seems to have lost its safe-haven attributes," said Ray Attrill, head of FX strategy at National Australia Bank.

"There is ... a loss of confidence to some extent ... you're overlaying that with the loss of exceptionalism and the view that in the short-term, at least, it's the US economy that's going to be suffering more than any other from what's happening on the tariff front."

The dollar, already on course for its worst year since 2017 , on Friday plunged to a decade-low against the Swiss franc and dropped to its weakest level against the euro in more than three years."The whole premise of the dollar as a reserve currency is being challenged, effectively, by what we've seen since Trump's election," said Attrill.

It was the establishment of the Bretton Woods system in 1944 that cemented the greenback's global standing. Post-war planners devised a system built on exchange rate stability and deepening international trade and the dollar remained dominant even after Bretton Woods broke down in the early 1970s.

But Trump's recent moves on trade have shaken perceptions. In a matter of days he has imposed hefty tariffs on the world, made an abrupt U-turn on his decision and intensified a trade war with China, throwing into question the reliability of the US administration.

Stocks globally have shed trillions of dollars and world markets have gone into a tailspin.

"Regardless of how the next 90 days evolve, the US's international reputation has been eroded," ANZ group chief economist Richard Yetsenga said in a note.